Page 1 Wisconsin Department of Transportation
Transportation Planning Manual
Table of Contents
Chapter 9 Traffic Forecasting, Travel Demand Models and Planning Data
SECTION 1 – General Forecasting Protocols and Procedures
... 3Subject 1 – Introduction and Purpose ... 4
Subject 2 – Reasons for Forecasts and Travel Analysis... 6
Subject 3 – Roles and Responsibilities for WisDOT Forecasting ... 8
Subject 4 – WisDOT Roadway Traffic Forecasting ... 10
Subject 5 – Related Policies ... 23
SECTION 10 – Forecasting in Travel Demand Model Areas
... 25Subject 1 – Introduction and Usage Areas ... 26
Subject 2 – Conditions for Use and Department Involvement... 30
Subject 3 – Model Version Control ... 33
Subject 4 – Demand Model Roadway Forecast Techniques ... 39
Subject 5 – Travel Demand Models and TAFIS ... 44
Subject 6 – Travel Demand Models and Travel Simulation Models ... 47
Subject 7 – Related Policies ... 49
SECTION 20 – Wisconsin Travel Demand Models
... 50Subject 1 – Multi-County Travel Demand Models ... 51
Subject 2 – Countywide Travel Demand Models ... 55
Subject 3 – Regional Travel Demand Models ... 59
Subject 4 – Sub-Regional Travel Demand Models ... 61
Subject 5 – Cross-State Regional Travel Demand Models ... 62
Page 2
SECTION 30 – Traffic Analysis Forecasting Information System (TAFIS)
... 65Subject 1 – Introduction and Usage Area ... 66
Subject 2 – Roadway Traffic Forecasting using TAFIS ... 69
Subject 3 – Enterprise Data Updates ... 78
Subject 4 – TAFIS and Meta-Manager ... 81
Subject 5 – Local Road Traffic Forecasting ... 83
Subject 6 – Related Policies ... 84
SECTION 40 – Data Elements of Roadway Traffic Forecasting
... 85Subject 1 – Introduction ... 86
Subject 2 – Estimating Vehicle Miles of Travel ... 87
Subject 3 – Geometric Design Factors ... 89
Subject 4 – Continuous Count Data and Adjustment Factors ... 99
Subject 5 – Truck Analysis for Traffic Forecasting ... 102
Subject 6 – Related Policies ... 105
SECTION 50 – Traffic Impact Analysis (TIA)
... 106Subject 1 – TIA Forecasts ... 107
Subject 2 – TIA Review ... 118
Subject 3 – Wisconsin TIA Guidelines ... 120
Subject 4 – Related Policies ... 125
SECTION 60 – Travel Surveys
... 126Subject 1 – Reasons for Collecting Data... 127
Subject 2 – Types of Surveys ... 130
Subject 3 – WisDOT Roles and Responsibilities ... 138
Subject 4 – Tasks to Conduct Travel Surveys ... 140
Subject 5 – Travel Survey Frequently Asked Questions... 142
Subject 6 – Related Policies ... 146
SECTION 70 – Other Planning Data
Subject 1 – Introduction Subject 2 – National Household Travel Survey (NHTS) Data Subject 3 – Census Data Subject 4 – Land-use Forecasting Subject 5 – Non-Auto Travel Modes Subject 6 – Web Applications Subject 7 – Related PoliciesSECTION 80 – Appendix
... 147July 2013 Page 3
Chapter 9:
TopTraffic Forecasting, Travel Demand Models and Planning Data
Section 1 – General Forecasting Protocols and ProceduresSubject
No. Subject Title Effective Date
Section 1 (All Subjects)
1.1 Introduction and Purpose December 2012 1.2 Reasons for Forecasts and Travel Analysis December 2012 1.3 Roles and Responsibilities for WisDOT Forecasting July 2013 1.4 WisDOT Roadway Traffic Forecasting April 2015 1.5 Related Section Policies July 2013
December 2012 Page 4
1.1 Introduction and Purpose
The Wisconsin Department of Transportation (WisDOT) has produced transportation forecasts and analyses for many years. Over the course of the last 20 years, WisDOT has refined techniques, developed policies and standardized procedures that have guided transportation analyses. Today, several sophisticated models and tools exist to forecast travel on Wisconsin’s transportation system. Chapter 9 - Traffic Forecasting, Travel Demand Models and other Planning Data outlines WisDOT’s forecasting process, from input assumptions to final output results. It explains why data quality matters, and where data quality might affect the accuracy of travel and traffic projections.
The purpose of this chapter is to formalize and standardize the process, requirements, and background information used to do traffic forecasting and multimodal travel projections in Wisconsin. It also serves as a reference for all parties who use traffic forecasts and travel demand estimation techniques in the corridor planning and project development processes. The ultimate goal of Chapter 9 - Traffic Forecasting, Travel Demand Models and other Planning Data is to communicate a high quality, streamlined process while making WisDOT procedures more transparent and accessible to a wide array of users.
This chapter:
Compiles forecasting documentation and provides applicable links to WisDOT resources, such as the WisDOT Facilities Development Manual (FDM) where more information can be found Serves as a record of policies, standards, and guidelines
Clarifies WisDOT expectations and procedures
Updates to this chapter will be made on an ongoing, as-needed basis. The chapter will change as policy, procedures, and/or work processes change within the Wisconsin Department of Transportation.
Transportation Planning Manual
Wisconsin Department of TransportationChapter 9, Section 1 General Forecasting Protocols and Procedures
Subject 1 Introduction and Purpose
Travel Demand Model Procedures Guide
ect 1 XDecember 2012 Page 5 Questions, comments, and other concerns on Chapter 9 - Traffic Forecasting, Travel Demand Models and other Planning Data can be directed to:
Jen Murray
Traffic Forecasting Section Chief
Wisconsin Department of Transportation
Phone: (608) 264-8722
Fax: (608) 267-0294
December 2012 Page 6
1.2 Reasons for Forecasts and Travel Analysis
Transportation forecasting is the process of estimating the number of people or vehicles that will use a specific transportation facility in the future. Transportation forecasts can be utilized in a variety of different situations and with different modes of transport, from estimating traffic volumes on a specific segment of road or highway to estimating ships in a port or passenger volumes on a city’s buses.
Forecasts explain what the needs of the future might be and provide benchmarks for proper
design and efficient transportation system operation.
Transportation forecasts are fundamentally important inputs in developing infrastructure – from developing overall transportation policy, to planning studies, to the engineering design of specific projects. Example applications of forecast information include: Development of infrastructure capacity and design calculations (e.g., the operations of an existing or proposed roadway or bridge, or the thickness or type of roadway pavements)
Estimation of the financial and/or social viability of projects (e.g., developing benefit-cost analyses and/or social impact assessments)
Calculation of environmental impacts, such as air and noise pollution
As noted in Section 1, Subject 3, travel analysis and traffic forecasts occur during long-range planning and during project development. WisDOT’s Traffic Forecasting Section provides expertise in the following analysis activities:
Highway traffic forecast assumption development and completion Regional travel demand and forecasting model development Travel and origin-destination survey implementation Vehicle miles of travel estimation
Special studies and analysis, including but not limited to
Transportation Planning Manual
Wisconsin Department of TransportationChapter 9, Section 1 General Forecasting Protocols and Procedures
Subject 2 Reasons for Forecasts and Travel Analysis
Travel Demand Model Procedures Guide
ect 1 XDecember 2012 Page 7 Traffic impact analysis (TIA) review
Seasonal factor review and update used to convert 48-hour traffic counts to estimates of Average Annual Daily Traffic (AADT)
Peak and design hour factors development Heavy truck classification estimation
July 2013 Page 8
1.3 Roles and Responsibilities for WisDOT Forecasting
The traffic forecasting section is the overall WisDOT business area lead in forecasting travel and conducting future travel analysis. The traffic forecasting section is physically located in WisDOT’s Central Office in Madison and is part of the Bureau of Planning and Economic Development (BOPED) in the Division of Transportation Investment Management (DTIM). WisDOT’s Southeast Region planning unit also directs traffic forecasting activities out of its unit, specifically for the Southeast Region. Traffic forecasting in the Central Office directs overall forecasting polices and implements travel analysis procedures. It conducts overall review and final approval of all forecasts. The traffic forecasting section mission is:
to add value to department planning, design and operations by transforming a wide array of traffic, demographic and economic data into traffic forecasts and related travel information essential to engineers, intercity and urban planners, project programmers and policy makers.
One part of the forecasting section responsibilities is to conduct highway traffic forecasts. Several transportation-related business areas use traffic analysis and forecasts. During long-range planning activities, Metropolitan Planning Organizations (MPOs) and WisDOT planners utilize forecasts to develop long-range transportation plans. Highway level-of-service criteria is discussed with highway programming and determined through predicted future conditions of travel demand. MPOs may also conduct analysis in urbanized areas with travel demand models to continually address transportation needs in their region. To demonstrate air quality conformity, forecasts of regional travel criteria affecting air emissions are compiled by WisDOT traffic forecasters and MPOs for the Environmental Protection Agency through the Wisconsin Department of Natural Resources.
WisDOT roadway traffic analysis occurs during planning and engineering. As transportation plans move to the project level, WisDOT region planners and project development engineers examine project scope
Transportation Planning Manual
Wisconsin Department of TransportationChapter 9, Section 1 General Forecasting Protocols and Procedures
Subject 3 Roles and Responsibilities for WisDOT Forecasting
Travel Demand Model Procedures Guide
ect 1 XJuly 2013 Page 9 and constraints with forecasted values. Forecasts provide a more detailed analysis of transportation mobility needs versus constraints. For example, during highway projects, engineers use traffic forecasts to implement more accurate designs; to better analyze intersection controls; to calculate roadway throughput; and to conduct pavement analysis.
It is WisDOT policy to utilize the traffic forecasting section and Southeast Region forecasters to participate in forecasting procedures for all modes of travel. While some analysis occurs at the region planning or MPO level (and in the Southeast Region, traffic forecasts are conducted in the planning section), WisDOT’s Central Office Traffic Forecasting Section conducts overall review and final determination of approval of all forecasts. Traffic forecasting maintains a record of approved forecasts for a minimum of five years. All forecasts should be submitted to the traffic forecasting section for review and approval. To ask for a forecast review, use form DT 1594. To submit a forecast request, use form DT1601.
Figure 1.3.1: All traffic forecasts are centralized
Statewide Traffic Forecasting
Southeast
Northeast
Southwest
Northwest
North
Central
April 2015 Page 10
1.4 WisDOT Roadway Traffic Forecasting
Each year, WisDOT completes hundreds of roadway traffic forecasts for corridor plans and projects. It is WisDOT policy to use a standard, multi-step traffic forecasting process and procedure to develop roadway traffic forecasts. Specifically, it is WisDOT policy to use the Traffic Analysis Forecasting Information System (TAFIS) to conduct roadway traffic forecasts, in all areas of the state, where no travel demand model exists; and to use a combination of TAFIS and travel demand model output to conduct traffic forecasts in areas where travel demand models do exist (See Section 10, Subject 4 and Section 30, Subject 1).
1.4.a. Process
As stated in WisDOT FDM Section 3-10-10, highway traffic forecasts are used for several reasons including to determine design standards, structural requirements and level-of-service analysis. It is WisDOT policy to conduct roadway forecasts on most federally-funded projects and state-funded local bridge projects. It is WisDOT policy that federally-funded local program construction projects, with average annual daily traffic volume of more than 500 vehicles, should be reviewed or conducted by WisDOT’s Traffic Forecasting Section or Southeast Region Traffic Forecasters, for Southeast Region projects. Accordingly, WisDOT policy requires forecasts for the following planning or project improvement types: Resurfacing Pavement replacement Reconditioning Reconstruction Capacity expansion Bridge replacement Access control Corridor studies
Transportation Planning Manual
Wisconsin Department of TransportationChapter 9, Section 1 General Forecasting Protocols and Procedures
Subject 4 WisDOT Roadway Traffic Forecasting
Travel Demand Model Procedures Guide
ect 1 XApril 2015 Page 11 If a state or local bridge or roadway project has documented proof of a current average annual daily traffic volume of less than 500, a WisDOT traffic forecast is not required. Designers can provide their own forecast. Designers may also request a forecast or review for projects under 500 if they do not possess the traffic expertise to perform the forecast.
If a bridge is not being expanded or replaced, then a forecast is not required. WisDOT FDM Section 3-10-10 exempts bridge rehabilitation projects. If significant traffic control is necessary, then a traffic forecast request should be submitted if it will help with project implementation. Because the life cycle of a bridge exceeds 30 years, it is important to design the bridge to accommodate increased traffic due to local development and to accommodate things like agricultural implements that might utilize the bridge.
In general, if local land use or development is anticipated to occur in the next five years and the traffic volume on the roadway is expected to exceed 500 AADT, then a forecast should be discussed with the department’s region traffic forecasting contact, who will determine whether to conduct a forecast. The region contacts are listed in Table 1.4.2.
Additionally, it is WisDOT policy to conduct forecasts at least twice during the life cycle of a project— once during project scoping/concept definition and then during data gathering of the final design. Please see WisDOT’s FDM 1 Attachment 1.1; FDM 5-3 Attachment 3.2 Project Scoping Checklist; FDM 3-20-5 Data Gathering.
It is imperative that designers request a forecast (and counts if needed) early in the life of a design project. Traffic data and forecasts will affect a project's pavement design, traffic analysis (if required), design study report, preliminary plans, project specifications and project cost estimates. WisDOT requires forecast documents for the project development process follow standard review and approval procedures.
WisDOT’s Central Office Traffic Forecasting Section conducts overall review and final determination of approval of all forecasts. This assures a consistent methodology is utilized (for more information on roles and responsibilities, see (Section 1, Subject 3). To request a forecast review, use form DT1594. To request a traffic forecast to be completed by WisDOT, use WisDOT form DT1601. These forms are filled out by the requester (often the project consultant, region planning or region project engineer) in
April 2015 Page 12 cooperation with the department’s region forecasting contact. The region contacts are listed in Table 1.4.2.
Region
Traffic Forecasting Contact
Telephone
1
Southwest
MADISON
LA CROSSE
MADISON/LA CROSSE - Jean Mancheski (F,
LR, TC) (608) 246-3807
MADISON/LA CROSSE - Graham Heitz (TIA) (608) 246-5362
2
Southeast
WAUKESHA
Robert Elkin (F) (262) 548-8704
Art Baumann (TIA) (262) 548-5626
Dan Malicki (TIA) (262) 521-5285
3
Northeast
GREEN BAY
Matthew Halada (F) (920) 492-7725
David Nielsen (TIA) (920) 492-0148
Kim Heise (TC) (920) 492-5985 or (920) 362-6360 4 North Central WISCONSIN RAPIDS RHINELANDER
WISCONSIN RAPIDS/RHINELANDER - Dave
Meurett (F) (715) 421-8348
WISCONSIN RAPIDS/RHINELANDER -
Richard Handrick (TIA) (715) 365-5716
5
Northwest
EAU CLAIRE
SUPERIOR
EAU CLAIRE-Richard Putzy (F, LR) (715) 836-2893
SUPERIOR-Martin Forbes (F)
(715) 392-7964
EAU CLAIRE/SUPERIOR-Jeff Olson (TIA) (715) 395-3031
Table 1.4.2: WisDOT Region Traffic Forecasting Contacts; (F) = Forecast Requests, (TIA) = Traffic Impact Analysis, (LR) = Local Road Count Info, (TC) = Traffic Counts
April 2015 Page 13 All appropriate data and attachments (including potential development information) are to be included in the forecast request to ensure a timely delivery or review of the traffic forecast. Once DT1601 or DT 1594 are completed, the region traffic forecasting contact submits it and related attachments to the Central Office Traffic Forecast Section, Vu Dang; Traffic Forecasting, BOPED, DTIM; Phone: (608) 266-2571; Email: [email protected]. Updates to WisDOT region forecasting contacts (see Table 1.4.2) should be sent to Vu Dang, as well. Table 1.4.2 will be revised on a continual basis in order to keep contact information current (last revised July 2013).
The traffic forecasting section (and WisDOT Southeast Region staff, in WisDOT Southeast Region) completes WisDOT’s traffic forecasts. Sometimes consultants working for WisDOT complete portions of traffic analysis for plans or projects. In these cases, WisDOT policy is to coordinate efforts between the consultant staff and the traffic forecasting section. Most of the time, WisDOT will supply a base forecast, including turning movement forecasts. A WisDOT project number (ID) will be assigned and appropriately charged. WisDOT’s Central Office Traffic Forecasting Section conducts overall review and final determination of approval of all forecasts. Forecasts not completed by the traffic forecasting section should be submitted for review and approval to the regional contact using the DT 1594 form.
To better understand how to fill out WisDOT form DT1601, see WisDOT FDM Section 3-10-10. Lack of data or an improperly filled out request form will be returned to the region traffic forecasting contact and will likely delay the process. Depending on complexity and traffic forecasting workload, it takes about four weeks to complete a forecast. Due dates of “as soon as possible” are not accepted, though all attempts to expedite a forecast will be made when resources allow.
1.4.b. Traffic Counts
WisDOT’s Bureau of State Highway Programs Data Management Section manages the statewide traffic count collection program. WisDOT uses current traffic counts or average annual daily traffic (AADT) as one of the main inputs to accurate roadway forecasts. WisDOT requires the use of the most recent count to develop the traffic forecast. WisDOT policy is to collect new traffic counts when the most recent count is more than three years old. Counts and forecasts performed by WisDOT are charged to the project and follow the improvement project agreement and normal cost sharing for design engineering. The project agreement should be consulted.
Depending on the situation and the type of forecast requested, traffic counts either exist in WisDOT enterprise data (called TRADAS) or exist in project data collection files at the region office. Mainline
April 2015 Page 14 traffic counts are traffic counts that are on continuous segments of the roadway network. Turning movement traffic counts are traffic counts at intersections; capturing the various types of turns occurring. All turning movement forecast requests must be accompanied by recent intersection traffic counts.
Traffic Counts Newer Than Three Years
AADT counts newer than three years should be attached to DT1601 when a traffic forecast is completed or requested.
New Traffic Counts
If traffic counts do not exist, AADT counts (and sometimes other traffic counts) must be collected before a forecast can be completed.
When
counts are older than three years, the traffic forecast requester should follow WisDOT traffic count data collection standards. All efforts should be made to ensure that new traffic counts are completed including all factoring for axles, day of week, season, etc. before the DT1601 is sent to traffic forecasting. Contact the Data Management Section at the Bureau of State Highway Programs for more information on factoring.1.4.c. Forecast Years
Forecast development usually assumes at least a 20 year planning horizon beyond the estimated time of construction. Multiple forecasts in one area should be coordinated by the region traffic forecasting contact to ensure that mid-forecast and final forecast years are coordinated across several forecasts, when possible. Forecasts include future average annual daily volume projections, hourly design factors for highway geometric design, heavy truck classification estimates for pavement design, and turning movements for intersection improvements.
1.4.d. Other Data Collection Requirements
To minimize the need for re-work, as much information as possible should be included in the original forecast request regarding recent new developments, newly constructed local arterial/collector streets, and recent major business expansions or contractions. Other data to be included with form DT1601 is listed in WisDOT FDM Section 3-10-10, Data Collection Techniques.
When a request is made in a Metropolitan Planning Organization area, the process and tools to develop the traffic forecast are essentially the same. Typically a travel demand model and the Traffic Analysis Forecasting Information System are used for travel behavior analysis. Sometimes, consultation with the MPO or local unit of government assists in data gathering and future planning activities and can have
April 2015 Page 15 some effect on the forecasted output. See Section 10, Subject 4 for more information on travel demand model forecast techniques.
After a traffic forecast is prepared, other data elements including peak-hour information, truck percents for the roadway, and other design parameters are investigated. See Section 40, Subject 1 for more information about the specific data elements of roadway traffic forecasting.
1.4.e. Roadway Traffic Forecasting Questions and Records of Older Forecasts
Discussions of upcoming forecasts between the design engineer and the traffic forecaster are also helpful when done well in advance of completing the forecast analysis. After a forecast is completed, if there are concerns or questions, please contact the traffic forecaster at the Central Office or in Southeast Region planning (if concerning a Southeast Region plan or project). There are situations where assumptions should be explained in detail. Many times the traffic forecasting contact will arrange a multilateral meeting or conference call to discuss the forecast. The traffic forecasting section does not adjust traffic forecasts based upon opinions. In the event the forecast question cannot be resolved, the traffic forecasting section chief will address the issue.
1.4.f. Types of Roadway Traffic Forecasts
Different types of roadway traffic forecasts are utilized in different situations. Forecasts are used for anything from determining future traffic volumes and turning movements at intersections (in order for traffic lights to have proper timing, for example) to providing traffic volumes and truck percentages so a roadway can be designed correctly for its capacity and material composition. Different types of forecasts are used to determine whether a future roadway should be planned for, designed, and built at a given location in order to accommodate future traffic volumes. Per WisDOT guidelines, several types of roadway forecasts exist, including but not limited to:
Roadway mainline (daily and peak forecasts)
Roadway turning movement (daily and peak forecasts)
Roadway mainline and turning movement forecasts for special land use analysis Traffic impact analysis (TIA)
Trip origin-destination or expansion analysis Trip generation studies
April 2015 Page 16 A forecast requester should review the needs of his or her project in order to properly submit the DT1601 form. The following section provides guidance and additional information regarding forecasts to the requester when he/she is determining the needs of the project. It also outlines forecast requirements.
Standard Design Year Forecasts
Standard design year forecasts (such as roadway mainline or turning movement forecasts) assume at least a 20 year projection into the future. Standard segment mainline forecasts are created with the Traffic Analysis Forecasting and Information System (TAFIS) and travel demand models (where available) and are the most basic type of forecast. If there is federal funding involved and the roadway traffic volume is more than 500 AADT, the following types of roadways require a forecast:
Resurfacings Pavement replacements Reconditionings Reconstructions Capacity expansions Bridge replacements, Access control projects Corridor studies
Model Alternative Forecasts
Model alternative forecasts usually use the same 20 year projection as standard forecasts. Model alternative forecasts are often created with travel demand models alone. Changes to model components, create changes to the model iteration process. New traffic volume results become part of project alternatives screening. Common screening components include and are not limited to:
Roadway number of lanes Roadway speed
Roadway access, new alignments, and bridge locations affecting traffic analysis zone loadings To compare project alternatives, model alternative forecasts are usually compared to the standard base forecast. Changes in assumptions or geometry are noted on the forecast report.
April 2015 Page 17
Traffic Impact Analysis: BASE Forecast and TIA DEVELOPMENT Forecast
A base traffic impact analysis (TIA) forecast is generally prepared if a proposed development is expected to generate more than 500 driveway trips during the peak hour, although region staff may determine that a forecast is required when the development generates more than 100 peak hour driveway trips (the threshold that triggers the need for a TIA). This forecast typically assumes a 30 year projection and forecasting techniques mimic the standard design year forecast process.
In addition to the base TIA forecast, to complete the TIA development proposal forecast, the number of trips generated by the proposed development in the peak hour must be added onto the base TIA forecast. To estimate site traffic that is added onto the base TIA forecast, several sources can be used:
The Institute of Transportation Engineers (ITE) Trip Generation Manual
A special study pertinent to proposed development showing future trip rates or individual company data
Local data from comparable developments
Other published references such as the ITE Journal
A trip generation study or studies conducted at similar sites that are like the proposed development
When completed, the base TIA forecast and the TIA development forecast are compared for logical growth rates. The TIA development forecast report should note where the source data for the number of trips in the peak hour came from and if any special techniques or assumptions were used to generate the numbers.
Extended Forecasts
Extended forecasts show full build out or increases in growth over and above the base. In these types of forecasts, future year may be indefinite. Full build out may mean increases to land use over and above what is assumed in the travel demand model. WisDOT does not always create or analyze future traffic volumes using an extended forecast. Examples when WisDOT might use an extended design forecast include:
April 2015 Page 18 In locations where projected base/standard design year volumes will meet the minimum
level-of-service soon after the design year
To identify opportunities to make small construction investments to account for additional capacity that might be needed just beyond the design year
Examples that have been noted using this approach include proposals showing:
A wider median, offset, lane, shoulder width and clear zone today, so that in the future it/they can be converted to a capacity lane
A wider shoulder underneath bridges so a capacity lane can be added later without reconstructing the bridge
Voluntary real estate preservation (not precluding future preferred alternatives) to prepare for the future additions of ramp turn lanes
The extended forecast may assume a 20 year up to a 40 year projection or may change population, employment, and land use growth projections. Traffic can be adjusted to test specific roadway carrying capacities or to test growth rates. Controlling factors that can be used to compare standard forecasts to extended forecasts include:
Basic roadway data (number of lanes, speed, roadway alignment)
Traffic conditions and level-of-service (access points, traffic lights, congestion, trip rates and others)
Land use change (urban, suburban, or rural)
Socioeconomics (population, average people in households, dwelling units and densities, employees and employment types, average autos per household, average daily person trips per household and others)
Transportation mode (mode of travel to work, mode tradeoff analysis and others) Special-generators (big box retail, schools, universities, and others)
An extended forecast should contain notes that explain applicable forecast perimeters and/or the controlling factors.
April 2015 Page 19
Standard Approach
Regardless if it’s a standard, model alternative, TIA or extended forecast—WisDOT creates forecasts using a standard forecasting procedure across the State of Wisconsin. The Bureau of Planning and Economic Development’s Traffic Forecasting Section records official forecasts in a database in Central Office. Anyone requesting forecast preparation must submit WisDOT DT1601 and pertinent information to WisDOT’s Region Forecasting Contact (see Table 1.4.2), who will submit the request to the traffic forecasting section. Anyone requesting forecast review and approval must submit WisDOT DT1594 and pertinent information to WisDOT’s Region Forecasting Contact (see Table 1.4.2), who will submit the request to the traffic forecasting section. Documented assumptions, context, and model changes used in the analysis or for any forecast submittal often include:
A standard forecast report showing base and future year traffic Traffic data, including peak hour volumes and truck percents Traffic forecast assumptions
Special procedures or trip generation techniques
Changes made during the analysis, including changes to roadway carrying capacity tests Control total determination procedures and reasonableness tests
Forecasts being used for a particular purpose should be compared against the standard design forecast. The traffic forecasting section (including the Southeast Region forecasters for forecasts in Southeast Region) will prepare, review and/or approve the forecast in a timely manner. If a forecast is revisited later, it will be imperative that the forecaster understand and be able to carry assumptions into future forecasts or analysis.
The following are examples of some of the forecasts completed by WisDOT’s Traffic Forecasting Section.
April 2015 Page 20
Roadway Mainline Daily Forecast
April 2015 Page 21
Roadway Turning Movement Daily Forecast
April 2015 Page 22
Roadway Mainline Forecast for Corridor Plan – Trip Origin-Destination or Expansion Analysis
July 2013 Page 23
1.5 Related Policies: General Forecasting Protocols and Procedures
A summary of the WisDOT policies that were discussed in this section are: It is WisDOT policy to:
Use a standard, multi-step traffic forecasting process and procedure to develop roadway traffic forecasts. WisDOT FDM Section 3-10-10
Conduct f
uture travel analysison roadways during corridor plan development; roadway
resurfacing,
pavement replacement, reconditioning, reconstruction, capacity and access control projects; and on bridge replacements. Utilize the traffic forecasting section and Southeast Region forecasters in the Southeast Region to participate in forecasting procedures for all modes of travel.
Conduct forecasts at least twice during the life cycle of a project—once during project scoping/concept definition and then during data gathering of the final design. WisDOT’s FDM 3-1 Attachment 3-1.3-1; FDM 3-5-3 Attachment 3.2 Project Scoping Checklist; FDM 3-20-5 Data Gathering.
Roadway traffic forecast requests (DT1601) are discussed, conducted, and reviewed by the traffic forecasting section (in WisDOT’s Southeast Region traffic forecasts are conducted by the region planning staff); overall approval is by the traffic forecasting section using form DT1594.
Use the Traffic Analysis Forecasting Information System (TAFIS) to conduct roadway traffic forecasts in all areas of the state where no travel demand model exists and use a combination of TAFIS and travel demand models to conduct traffic forecasts in areas where travel demand models exist.
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Subject 5 Related Policies: General Forecasting Protocols and Procedures
Travel Demand Model Procedures Guide
ect 1 XJuly 2013 Page 24 Conduct forecasts on all federally-funded plans or projects (even local projects), and all
state-funded local bridge projects that are currently more than 500 vehicles of average annual daily traffic and are not resurfacings.
Receive requests for traffic forecasts using form DT1601.
Receive requests to review traffic forecasts done by others using form DT1594. Maintain completed forecast records for a minimum of five years.
Collect new traffic counts when the most recent count is more than three years old.
Utilize traffic counts as one of the main methods for accurate forecasts and always use the most recent count to develop the traffic forecast.
Conduct a meeting with the traffic forecasting section chief and other management as needed, in the event a forecast issue cannot be resolved.
April 2015 Page 25
Chapter 9:
TopTraffic Forecasting, Travel Demand Models and Planning Data
Section 10 – Forecasting in Travel Demand Model AreasSubject
No. Subject Title Effective Date
Section 10 (All Subjects)
10.1 Introduction and Usage Areas April 2015 10.2 Conditions for Use and Department
Involvement April 2015
10.3 Model Version Control December 2012
10.4 Demand Model Roadway Forecast Techniques December 2012 10.5 Travel Demand Models and the Traffic Analysis Forecasting Information System
(TAFIS) December 2012
10.6 Travel Demand Models and Travel Simulation Models December 2012
April 2015 Page 26
10.1 Introduction and Usage Areas
Travel demand models are sophisticated tools used to forecast future travel patterns. Current socio-economic data, roadway networks, trip rates, and other factors are used by the model to calculate the current and future travel patterns on a transportation system. Trip-making behavior analysis, completed utilizing the outputs from travel demand models, is input into long-range plans. Used with other planning tools, travel demand models can output a variety of data, including roadway traffic forecast information and deficiency characteristics.
10.1.a. Travel Demand Model Four-step Process
Wisconsin’s travel demand models are based on a classic four-step process that consists of:
Trip generation: This step determines the frequency of origins and destinations of trips in each
zone by trip purpose, typically as a function of household demographics and land uses, and other socio-economic factors.
Trip distribution: This step pairs trip origins with destinations.
Mode choice: This step calculates the proportion of trips between each origin and destination that
use different transportation modes.
Traffic (route) assignment: This step allocates trips between an origin and destination by a
particular mode via different travel routes. Usually, route assignment is calculated under the assumption that each driver will choose the shortest travel time between origin and destination, subject to every other driver doing the same.
Where travel demand models exist, it is WisDOT policy to use travel demand models in combination with the Traffic Analysis Forecasting Information System (TAFIS) during roadway traffic forecasting procedures (see Section 10, Subject 4). Section 30, Subject 1 outlines forecasting procedures where travel demand models do not exist.
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Subject 1 Introduction and Usage Areas
Travel Demand Model Procedures Guide
ect 1 XApril 2015 Page 27
10.1.b. Metropolitan Planning Organizations and other Usage Areas
Fourteen MPOs exist in Wisconsin. These MPOs are responsible for transportation planning and programming activities in metropolitan areas that have more than 50,000 people. MPOs prepare long-range transportation plans, which require traffic forecasts with at least a 20 year planning horizon. WisDOT coordinates with the MPOs to develop and maintain travel demand models as part of this process. This also supports a comprehensive approach to local, regional, and state transportation planning. See Figure 10.1.1 for metropolitan planning areas and model locations. Chippewa-Eau Claire, La Crosse, and Dubuque have models that mirror the metropolitan planning area. Wausau, Janesville, and Beloit MPOs use travel demand models that mirror the boundaries in their respective counties rather than the smaller planning area boundaries. Madison utilizes a county-wide travel demand model, with the additional complexity of a mode-choice module. The MPOs located within WisDOT’s Northeast and Southeast Regions maintain regional travel demand models that encompass multiple MPO areas.
Travel demand models also exist in the non-MPO areas of Stevens Point, Wisconsin Rapids, and St. Croix County.
April 2015 Page 28 Figure 10.1.1: Travel demand models and Metropolitan Planning Areas in Wisconsin
April 2015 Page 29 Wisconsin’s travel demand models contain geographies called transportation analysis zones (TAZs). Each travel demand model has a unique TAZ system that aggregates land use activity at a scale comparable to U.S. Census block groups. The land use summary for each TAZ is used in the trip generation step of the model to determine its productions and attractions. Trip distribution converts the zonal productions and attractions to origins and destinations, while mode choice determines the method (transit or automobile) each trip will take. Trips are then routed along the transportation system in the traffic (and/or transit) assignment step of the model. The Dane County Model, Southeast Wisconsin Regional Planning Commission Model, and the Northeast Region Model are currently the only Wisconsin models that include a full mode choice and transit assignment component. Mode choice is accounted for with auto occupancy rates by trip purpose where transit options are available.
Currently Wisconsin’s travel demand models (except Dubuque, Duluth-Superior and the Southeast Region Planning Commission travel demand models) are coded with unique location identification codes that are integrated with WisDOT’s Traffic Data System (TRADAS). This allows traffic counts and other inputs to be entered more easily, and outputs to be extracted and compared with other forecasting methods (especially TAFIS, as described in Section
10
, Subject5
).Travel demand models have been developed:
Using Citilabs’ Cube TP+ scripting platform to produce daily traffic forecasts Integrating National Household Travel Survey add-on data
Using data gathered from the U.S. Census Using a traditional four-step model process Following MPO long-range plan update cycles
As stated in Section 1, Subject 4, the traffic forecasting section at WisDOT approves and stores a copy of all official roadway traffic forecasts in Wisconsin to make sure that reliable estimates of traffic movements are accounted for across the state. WisDOT travel demand models provide input into the traffic forecast, including origin and destination trip tables that can be used for input into traffic micro-simulations (e.g., Paramics, Corsim). See Section 1, Subject 4 and WisDOT FDM Section 3-10-10, for more information about roadway traffic forecasts.
April 2015 Page 30
10.2 Conditions for Model Use and Department Involvement
Urban travel demand models represent a significant investment by the State of Wisconsin. Once constructed, it is in the public’s interest to apply the models to their maximum potential. Primary users of the travel demand models include consultants, MPOs, and WisDOT regional staff, though the models are available for use to others, as well.
10.2.a. Conditions for Model Use
Wisconsin Department of Transportation has identified model standards and expected practices and procedures for model use. Those requesting release of MPO model data (termed, the user) from the Wisconsin Department of Transportation (referred to as, the department) should understand the purpose and limitations of each model before using the data.
These procedures are to be followed for every project and by every user, regardless of prior model usage or approval.
A. The user of model data shall complete a DT1599 form and submit the completed form to the department’s traffic forecasting section. The contact is:
Vu Dang
Traffic Forecasting Section
Wisconsin Department of Transportation Phone: (608) 266-2571
Fax: (608) 267-0294
Email: [email protected]
B. The model input data and associated files as well as materials and data developed from the model should not be applied by the user beyond the intended use and agreed-upon terms in the DT1599 form.
C. Users of the model must obtain and maintain their own licensed copy of the platform software (i.e., CUBE Voyager).
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Subject 2 Conditions for Model Use and Department Involvement
Travel Demand Model Procedures Guide
ect 1 XApril 2015 Page 31 D. The user shall not distribute the model or any files associated with the model to anyone outside
the department, unless authorized by the department’s traffic forecasting section.
E. If the model socio-economic data needs to be amended or updated by the user, a written authorization must be obtained from the traffic forecasting section who will consult with the applicable Metropolitan Planning Organization.
F. Upon completion of its intended use, the user will agree to terminate the usage of the model(s) and all associated information and files unless other arrangements are agreed to by the department’s traffic forecasting section.
G. Upon completion of the project, the user agrees to provide copies of the final model files for the department and Metropolitan Planning Organization records. This includes, but is not limited to:
a. All input files b. Executables c. Output files
H. The user agrees to deliver the items listed in Part G in the same file format obtained from the department or as specified by the department’s traffic forecasting section.
I. The user agrees to provide a document identifying all files edited and a description detailing how and why the files were modified.
J. The department accepts no responsibility for the results of the model application and/or model data maintained by the user.
K. Cooperation with the department (WisDOT region and the traffic forecasting section) is required throughout the course of a project and specifically recommended at the following phases of a project:
a. Initial kick-off meeting: Review proposed project-level forecasting methodology and establishment of travel demand model assumptions
b. First project meeting: Review model validation prior to draft forecasts c. Second project meeting: Draft and final forecast review, prior to presentation
d. Final project meeting: Delivery of all model use documentation and electronically updated modeling files.
L. It is WisDOT policy that if a model change is deemed necessary (see Section 10, Subject 3), model files and elements will be transmitted to the department or vice-versa. Any model updates shall be consistent with the standardized model nomenclature outlined in Chapter 80, Subject 1, unless previously authorized by the department.
April 2015 Page 32
10.2.b Department Involvement
Valid assumptions lead to credible forecasts. WisDOT’s Traffic Forecasting Section requests project milestone meetings, as applicable and as indicated in Part K. The traffic forecasting section leads interim reviews and directs model application procedures. See Section 10, Subject 4 for more information.
WisDOT’s Central Office Traffic Forecasting Section conducts overall review and final determination of approval of all forecasts. It is WisDOT policy that any forecasts completed using the travel demand models or their outputs, without following the procedures outlined above, will not be considered for approval. Please see Section 1, Subject 3 for more information regarding roles and responsibilities during the traffic forecasting process
December 2012 Page 33
10.3 Model Version Control
The Wisconsin Department of Transportation Traffic Forecasting Section is responsible for model version control on the travel demand models. The forecasting section houses and maintains the latest travel demand models. The department works closely with each MPO to develop and maintain each MPO’s regional travel demand model. The traffic forecasting section manages and approves all changes to the travel demand models in Wisconsin, except for Dubuque, Duluth-Superior, and the Southeast Regional Planning Commission travel demand models. All model requests and submittals should be made to the department. Coordinate all usage of the travel demand models with WisDOT traffic forecasting section as outlined in Section 10, Subject 2. Ongoing involvement from the MPOs on a variety of issues occurs.
10.3.a. Model Documentation
Travel demand models can change. Listing out the changes that have been made helps to eliminate confusion and increases user confidence in model results. It also minimizes duplicative efforts that may result from users not having a clear understanding of previous changes. Documentation is kept in a library of model updates at WisDOT’s Central Office Traffic Forecasting Section. Documentation occurs in three general areas, highway/transit, land use and model parameters. Documentation should clearly identify model version and the date the model was received from WisDOT and/or the MPO. WisDOT traffic forecasting will allow the use of graphics (i.e. area type, travel lanes, etc.) to support documentation of the model changes.
10.3.a.i. Network Updates
The transportation system should be accurately represented in the regional travel demand models. At a minimum, the transportation system should represent the system’s existing conditions. Committed projects in the model represent projects that have been approved and have the funding for implementation. MPOs are federally required to update their transportation improvement program (TIP) yearly and provide a coordinated listing of the short-range transportation improvement projects
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Subject 3 Model Version Control
Travel Demand Model Procedures Guide
ect 1 XDecember 2012 Page 34 anticipated to be undertaken within a five year time horizon. These are the committed projects. Project prioritization often occurs during TIP development.
Planned projects in the model are defined as projects that do not have approval or funding for implementation. The TIP can be used to determine the status of anticipated projects and for classification as committed or planned within the model. The planned transportation system should be consistent with the long-term vision outlined in the MPO’s long-range transportation plan, if the travel demand model is within an MPO planning area. Additional projects can be added and tested on a project-by-project basis to develop traffic forecasts and are often referred to as transportation alternatives. When conducting traffic forecasts, usually forecasts are developed for an MPO’s Existing plus Committed (E+C) network, but not for an MPO’s Existing plus Committed plus Planned (E+C+P) network.
WisDOT’s Traffic Forecasting approves changes to the network, after consultation with the region and the MPO. Input from local stakeholders is recommended, but not required. Documentation should reflect the inherent uncertainty of travel behaviors and decisions over time and the impact they can have on forecasts developed using the travel demand models.
Documentation of updates to the highway network should include but is not limited to the following: Addition or removal of roadway facilities
Functional classification updates Travel lane updates
User-speed overrides
Newly committed and/or planned projects
10.3.a.ii. Land Use Updates
Land use assumptions developed for the MPO travel demand models are dynamic and continuously changing. Proper representation of the land use assumptions play a critical role in the model development and application. At a minimum, any changes to land use shall represent consistency with the local comprehensive plan. Employment, population, and/or housing numbers are often used as control totals in the travel demand modeling process. Municipal control totals shall be consistent with the local comprehensive plan and/or with data published by the Wisconsin Department of Administration’s Center for Demographic Services. The travel demand models that WisDOT manages use the future projected
December 2012 Page 35 Wisconsin Department of Administration’s Center for Demographic Services’ population figures as a control total for future year growth in the models.
WisDOT’s Traffic Forecasting Section approves land use changes in cooperation with the region and MPO staff. Often, better land use estimation occurs with local stakeholder input. Document land use changes to better recognize how the changes affect long-range socio-economic forecasts. Changes to the model land use data will ultimately change traffic forecasts.
Document land use changes clearly. Submit a table of existing and updated land use assumptions to WisDOT’s Traffic Forecasting Section when they have occurred. Document zonal adjustments or expansions with an illustration to better represent changes for traffic forecasting section approval.
Documentation of updates to the land use should include but is not limited to the following: Addition or expansion of zonal system (graphic required)
Control total updates
Household, employment or school enrollment updates Special generator updates or additions
10.3.a.iii. Transit Network Updates
Proper representation of transit routes and assumptions play a critical role in the development of ridership forecasts. At a minimum, transit updates shall be consistent with the latest service planning assumptions and be consistent with the plans developed by the appropriate transit agencies.
WisDOT traffic forecasting approves transit system updates with assistance and cooperation from the region, MPO, and input from local stakeholders. Documentation of model changes should reflect the inherent uncertainty of long range transit forecasts. Key uncertainties include these factors—transit accessibility, competing services, regional development assumptions, mode bias, and transit fares, all of which can impact forecasts developed using the travel demand models.
Documentation of updates to the transit network should include but is not limited to the following: Addition or removal of transit routes
December 2012 Page 36 Run time (i.e. service hours and bus speed)
Headway
Future service improvements
10.3.a.iv. Trip Generation and Distribution Updates
Calibrated model parameters represent estimated travel behaviors and choices in a mathematical context. Adjustments to model parameters should be completed in direct accordance with and submitted to WisDOT Traffic Forecasting Section due to the large impact they have on the model outputs. Submit tables providing the existing and updated model parameters. If model parameters are determined to have a significant impact on regional travel behaviors, a validation report must be submitted consistent with Section 10, Subject 3.b.
Documentation of updates to model parameters should include but is not limited to the following: Trip generation rates
K-factors Friction factors
Mode-choice coefficients Auto-occupancy rates Time of day factors Volume/delay coefficients
10.3.b. Validation Reports
1Model validation refers to the application of a calibrated base year travel demand model, and the corresponding comparison between modeled results to observed data. A review of validation criteria enables a travel demand model user to determine if the model is performing at a level that produces appropriate results. The model should replicate observed travel behaviors without adversely affecting the ability to forecast the transportation project alternatives’ attributes or characteristics. Well-documented validation results provide travel demand modelers with information necessary to determine the amount of
1 Model validation procedures rely heavily on information provided in the Travel Model Improvement Program
December 2012 Page 37 confidence that can be placed in the model outputs. WisDOT’s Traffic Forecasting Section expects model-wide or project level basis documentation.
Document inherent model limitations and provide a concentrated validation overview. An overview of updates and a corresponding validation report must be provided to WisDOT’s Traffic Forecasting Section to establish benchmarks for model performance.
In project documentation, fully disclose updates to regional, corridor, and site level corridor plans or projects and provide a summary of the validation reports produced after running the regional travel demand model. Establish and explain the difference between the baseline (existing) and updated model. When counterintuitive results are reported, provide an explanation of them.
Validation reports should include but are not limited to the following: Average daily traffic summary
GEH summary
Root mean square error report Screenline report
Model AADT to observed AADT
Ridership to on-board survey for transit, if applicable
Contact WisDOT’s Traffic Forecasting Section for more information on validation reports. Validated base year models ensure the model is able to reasonably reflect future year conditions. Validation of a base year model does not, in itself, ensure the reasonability of the future year forecasts. The validation process compares phases and aids in the development of credible forecasts. The process may differ slightly on a project-by-project or transportation mode basis. Document all methods and procedures and verify with WisDOT’s Traffic Forecasting Section procedures to ensure consistency across the state.
10.3.c. Forecast Documentation
When completing a traffic forecast, WisDOT’s Traffic Forecasting Section requires documentation of travel demand model input and output changes, that may have occurred, as well as any other procedures deviating from normal practices or procedures. To understand how to develop a forecast with travel demand model data, please see Section 10, Subject 4. Ultimately, as stated in Section 10, Subject 1, WisDOT policy is to use travel demand models in combination with TAFIS during roadway traffic
December 2012 Page 38 forecasting procedures where travel demand models exist. All forecasts created using Wisconsin’s travel demand models must be approved by the traffic forecasting section.
December 2012 Page 39
10.4 Demand Model Roadway Forecast Techniques
Travel demand models are a very useful tool in traffic forecasting, particularly in alternatives analysis forecasting and in forecasting growth based on specific socioeconomic factors. As stated in Section 10, Subject 1, WisDOT policy is to use travel demand models, in combination with the Traffic Analysis Forecasting Information System, during roadway traffic forecasting procedures where both exist. Utilized for a wide range of projects, ranging from statewide forecasts to sub-area studies involving micro-simulation models, travel demand models require initial confidence in data assumptions and careful interpretation of model outputs. Several steps are involved in generating a model output. These include and are not limited to:
Reviewing model assumptions
Changing attributes and revalidating the model (if applicable) Adjusting the assignments for forecast development
Adjusting roadway link growth rates Finalizing the roadway traffic forecast
It is WisDOT policy to document travel demand model and Traffic Analysis Forecasting Information System processes, steps, and assumptions to support logical forecast outputs.
10.4.a. Reviewing Model Assumptions
Roadway traffic forecasts are generally created the same way, regardless of the scale of the model. To be valid across forecast types, model assumptions should be reviewed. At the regional, corridor, site, or the long-range plan levels, several attributes should be reviewed before forecast development. The base year is defined as the year all data has been collected and usually corresponds to decennial U.S. Census data collection year—2000, 2010, 2020, etc. The future year is usually the travel demand model forecast year
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ect 1 XDecember 2012 Page 40 that corresponds with the MPOs long-range plan horizon year. The following attributes should be reviewed:
Traffic analysis zones
o Base and future year employees per zone
o Base and future year houses or population per zone o Centroid connections
Base and future year transportation network assumptions o Functional classification
o Speed, including travel-time estimations o Roadway network capacity
o Roadway network lanes
o Operational characteristic review
Connectivity with other roadways
Surrounding roadway characteristics of influence
Existing projects, future year STIP and TIP committed projects and planned MPO projects In addition to the above, at the corridor and site planning levels, travel demand models require a review of the following at a minimum:
Future year local comprehensive plans or development plans Base and future year trip generation assumptions
Base and future site-specific travel times or origin-destination pairings
During long-range plan development all of the above mentioned items are reviewed in depth, and any changes must be made in accordance with Section 10, Subject 3. WisDOT assists MPOs in updating models as part of the long-range transportation plan update every five years (every four in air quality non-attainment areas). At a minimum, every long-range plan update requires transportation network and socio-economic data (households and employment) review. MPO staffs are able to utilize travel demand models to evaluate urban growth and transportation investments to evaluate future improvements on a regional level.
December 2012 Page 41 If after reviewing model assumptions it is determined that no changes to the model are necessary, the analyst should determine the appropriate adjustment to be applied to the model assignment for forecast development. If it is determined that changes are needed to the model to continue forecast development, the analyst should change attributes and revalidate model.
10.4.b. Changing Attributes and Revalidating Model (if applicable)
When modifications are necessary to the travel demand models for roadway traffic forecast development, see Section 10, Subject 3 for procedures. Once approval is granted from the traffic forecasting section, the forecast development can proceed.
10.4.c. Adjusting Assignments for Forecast Development
Because of the difficulty in calibrating and validating travel demand models, the raw traffic assignment, or traffic that is assigned to a roadway link, is often misrepresentative of the actual traffic volumes. This phenomenon is usually evident in the model’s base year and can be tested by comparing the raw base year traffic assignment to the counts on corresponding road segments or travel demand model links.
Usually, a factor in a travel demand model can cause a raw roadway assignment value to be higher than the traffic count in the base year. This can also cause the future roadway traffic assignment to be high (over-assignment). Low traffic count assignment values can also affect model results, creating assignments that are lower than the corresponding counts (under-assignment). To account for the differences between assignments and roadway traffic counts in the base year, a set of methodologies was produced by the Transportation Research Board and published in the National Cooperative Highway Research Program Report #255 Highway Traffic Data for Urbanized Area Project Planning and Design. The methodologies in this report set a standard for adjusting the raw future year roadway traffic assignments (or raw long-range plan horizon year traffic) based on the base year traffic assignment and count values. It is WisDOT policy to follow standard, well-researched, nationwide protocols. Current methodologies are subject to review and/or replacement in light of the development of new standards.
The first method presented in the NCHRP report is called the difference adjustment method, which adjusts the future year assignment based on the absolute difference between the count and the base year assignment. The equation is as follows:
Difference Adjustment:
